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Introduction of Nuclear Power Plant (NPP)

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Currently, approxi.17% of electricity worldwide isproduced by nuclear power plants.

France, over 75% of their electricity is produced by

nuclear power. The United States, produces about 15% ofthe electricity from nuclear power.

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NPP in France (75% total production)

France is the world's largestnet exporter of electricitydue to its very low cost ofgeneration, and gains overEUR 3 billion per year fromthis.

Reactors and fuel productsand services are a majorexport. About 17% ofFrance's electricity is fromrecycled nuclear fuel.

Thn: 2013

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Thn: 2006

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(1) Fuel : This can be either fissile material (233U, 235U,239Pu, 241Pu) or fissionable material (232Th, 238U,240Pu). Most modern NPP utilize this fuel in a ceramicform - oxide (UO 2), carbide (UC), nitride (UN).

(2) Fuel element : The smallest sealed unit of fuel. In

LWR/LMFBR the fuel element is a metal tubecontaining ceramic pellets of fuel. In HTGR, its can be atiny particle (300um in diam.) of UC coated withpyrolytic graphite layers

(3) Fuel assembly or bundle : the smallest unit combiningfuel elements into an assembly. In LWR, the fuelassembly is composed of several hundred fuelelements fastened together at top and bottom

Components of nuclear reactor system

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(4) Moderator : Material of low mass number which is insertedinto the reactor to slow down or moderate neutrons viascattering collisions. Typical moderators: light water, heavywater, graphite and beryllium

(5) Coolant : A fluid which circulates though the reactorremoving fission heat. The coolant can be either liquid(water, sodium) or gaseous (helium, carbon dioxide). It may

serve a dual role as both coolant and moderator (in LWR)(6) Coolant channel : One of the many channels through which

coolant flows in the fuel lattice(7) Structure : The geometry and integrity of the reactor core is

maintained by structural elements such as support plates,spacer grids, metallic tube used to clad the fuel

(8) Control elements : absorbing material inserted into thereactor to control core multiplication (ex. Boron, cadmium,gadolinium and hafnium)

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(9) Reactor core : the total array of fuel, moderator and controlelements

(10) Reactor blanket : In a breeder reactor, the core is usuallysurrounded by a blanket of fertile material that moreeffectively utilized the neutron leaking out of the core

(11) Reflector : A material characterized by a low absorptioncross section used to surround the core in order to reflector scatter leaking neutrons back to the core

(12) Shielding : Absorbing material introduced to attenuateboth neutron and gamma radiation (radioactive protection)

(13) Support structure : The support plates that serve tomaintain the core geometry

(14) Reactor pressure vessel : The high pressure containmentfor reactor and associated primary coolant system

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Comanche Peak Power Plant, Glen Rose, TX USA Source: P. A. Scholle & D. S. Ulmer-Scholle, 1997

Reactor pressure vessel

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radioactive zirconium-coated rods withuranium pellets immersed in water

Water as a coolant andmoderator

Control rod serves to

maintain k factor

Fuel rod

contains pellet

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The blue glow in the watersurrounding nuclear reactors isCherenkov radiation. The wateris there to stop neutrons; butneutrons are uncharged and sodo not themselves directly causethe radiation. The Cherenkovradiation actually comes frombeta particles (fast electrons)emitted by fission products.

This effect, known as Cherenkov radiation , was observed as a faint blue glow byPavel Cherenkov in 1934 when he was asked to look at the effects ofradioactivity in liquids. The explanation for the light was provided by Ilya Francand Igor Tamm. It is possible to detect the Cherenkov radiation as it formscircles on a surface, and it can be used to measure the speed and direction theparticle was travelling in. It is therefore a very useful means of studying theproducts of particle collisions and cosmic rays.

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Refueling the Reactor Core Source: P. A. Scholle & D. S. Ulmer-Scholle, 1997

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Uranium ore (99.3% of238U and 0.7% 235U)

Oxides

Carbides

Nitrides

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The pebble bed nuclear reactor. heliumgas is used to cool the spherical fuelelements

Fuel rod

Geometrical configuration of fueland cladding1. Fuel rod2. Fuel Plate3. TRISO pellets

Fuel plate(Advance Test Reactor)

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Nuclear power plants use pellets to fuel the plants.A pellet contains approximately 3% U-235 that isencased in a ceramic matrix.

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Coolant and Moderator

Coolant system:1. Primary Coolant system

2. Secondary Coolant System

In LWR water serve ascoolant and moderator

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Liquid Sodium serve as acoolant, other candidate isliquid lead-Bismuth (Pb-Bi)

Fast Breeder Reactordoesnt need a moderator

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The characteristics of liquid metals as coolantcandidates for NPP